基于循环灰热载体煤热解的固-固颗粒冷态混合特性

Cold mixing characteristics of solid particles based on the coal pyrolysis with circulating ash heat carrier

以开发循环流化床(CFB)燃烧/煤热解分级转化工艺为应用背景,为在移动床混合段内利用有限高度空间达到理想的灰/煤混合效果,建立了内置锥面形挡板结构的固-固冷态混合实验装置,并对颗粒的混合特性进行了研究。分别以石英砂和硅胶模拟CFB循环灰和煤,采用挡板重力混合的方法,探究了挡板角度、层数、放置方式(对向和旋转放置)以及物料混合比等因素对混合效果的影响,并与机械混合实验进行了对比。结果表明,在混合过程中颗粒的混合和分散是并存的,旋转放置30°的挡板层数越多,硅胶和石英砂颗粒混合越均匀,混合物料中石英砂比例越高,混合效果越好。通过优化挡板结构及设置方式强化对流混合和剪切混合可明显改善固-固混合效果。虽然与机械混合相比,挡板混合效果略差,但在一定操作范围内仍可满足灰/煤混合热解工艺的要求。

To develop a step conversion process of coal pyrolysis/circulating fluidized bed（CFB）combustion,this paper focuses on realizing an optimal ash/coal mixing effect of moving bed within a limited height space of mixing section. A solid-solid cold mixing apparatus with adjustable cone shaped baffles inside was built and the mixing characteristics of particles were studied. Silica and quartz sand were used to simulate coal and circulating ash heat carrier from CFB,respectively. The influences of the material mixing ratio,the angle of baffles,the number and placement method（opposite and revolving）of baffles on mixing effect by using gravity mixing method were investigated,and the results were compared with those achieved by mechanical mixing. Mixing and dispersing coexist in the process of particles mixing. It was found that the more layers of 30°baffle by revolving placed,the more uniform of the silica and quartz mixture. The uniform mixture was obtained at the higher proportion of quartz sand to silica. Optimizing baffle structure and setting mode enhances convection mixing and shear mixing,which improves the solid-solid mixing effect obviously. Although the mixing effect of the cone shaped baffle is slightly worse compared with that of mechanical mixing,baffle mixing can still meet the requirements of the ash/coal mixing operation of coal pyrolysis with a solid heat carrier.